It is a known fact that crude palm oil is rich in carotenes, a class of C.sub.40 polyunsaturated hydrocarbons. Commercially cultivated oil palm yields crude palm oil which contains 500-700 ppm carotenes of which .alpha. and .beta. carotenes comprise 90% of the total carotenes. However, newer clones or new species of oil palm trees can produce crude palm oil with carotene concentrations of 1000-3000 ppm. The carotenes are known to posses pro-vitamin A properties and recent findings have shown that .beta.-carotene also inhibits tumor progression and hence, reduces cancer formation in animals, including humans. At present, edible palm oil is used in the refined, bleached and deodorized form. However, the refining process of producing refined, bleached and deodorized form of oil commonly adopted in palm oil refining industry results in the carotenes being destroyed, while the oil is being deodorized and deacidified. The refined oil of the prior art process normally has a free fatty acid (FFA) content of less than 0.1%, carotene content of less than 20 ppm and color of less than 3 red in a 5 1/4" cell (Lovibond Scale). Prior art refining process of crude palm oil in summary involved, deodorizing at temperatures between 240.degree. C.-260.degree. C. and at a pressure of 1-3 torr which processes resulted in not only the removal of unwanted fatty acids, but also all carotenes being destroyed. Moreover, .alpha.-, .beta.-,.gamma.-, and z-(zeta), zeacarotene, cis .alpha.-carotene, cis .beta.-carotene and lycopene are all destroyed.
In prior art plant configurations, degassing of the crude palm oil and deodorizing of the degassed oil is done within the same equipment. The typical operating temperature is between 240.degree. C.-260.degree. C. At these temperature levels, unwanted free fatty acids (FFA) are removed. However, all the carotenes are also broken down. If the operating temperature is lowered, the FFA are not completely removed to meet the specification stipulated for edible oil. The end product is not completely deodorized and the taste is not bland.
In recent times, attempts have been made to produce refined palm oil wherein the naturally occurring carotenes and Vitamin E are retained in substantially large quantities. For example, Australia Patent No. AU-B-31084189 (AU'189) granted to Palm Oil Research Institute of Malaysia, discloses an improved process for the refining of edible palm oil substantially without destroying the carotenes present in the oil. The prior art process comprises the step of subjecting the oil to a pressure of less then 0.060 Torr and a temperature of less than 200.degree. C. According to this prior art invention, palm oil or a product of palm oil is passed through a deodorizer, preferably at a temperature in the range 100.degree. C.-200.degree. C. and at a pressure in the range of 0.003-0.06 Torr. During this process, the free fatty acids are distilled over and the oil deodorized, but the carotenes are not destroyed. This deodorized palm oil has a free fatty acid content of less than 0.12%. Carotene content and peroxide values are almost the same as before the process. The refined oil has a bland smell. The examples disclosed in the Australia patent are restricted to a laboratory scale. However, on repeating the Australian process on a pilot plant scale or on a commercial plant scale, the FFA and carotene content changed dramatically. It was not possible to obtain yields of refined palm oil with the characteristics disclosed in the AU'189 on a scale greater than simple laboratory amounts, which are less than 10 kg/hr.
It is believed that gas, lights and free fatty acids at the molecular distillation stage create a strain on the distillation process. Increasing the operating temperature at the molecular distiller reduces the level of FFA in the refined oil, but at the same time destroys the carotene content in the oil. At operating temperatures between 100.degree. C.-200.degree. C. and at 0.003-0.060 Torr, all the FFA is not removed due to inefficient removal of condensed FFA in the condensation column.
In view of the foregoing, what is needed in the art is a refining process wherein the FFA are removed to an acceptable level, the oil is deodorized to an acceptable level and the oil is rendered tasteless. Moreover, a refining process is needed wherein the level of the carotene and Vitamin E present in the preprocessed crude palm oil is retained in the refined oil and the crude palm oil is refined at a rate greater than laboratory scale. The present invention fulfills these and other needs.